[Hold for pipeline test] Support control-flow

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• ONNX frontend
  • [x] Refactor GraphConvert
  • [x] Loop op convert
  • [x] If op convert
  • [ ] Refactor
• Fix benchmark convert problems
  • [ ] GatherV2 check failure (temporally comment generic_op translate function to bypass this problem)
  • [ ] Support ScatterND (TODO: cuda kernel emitter)
• NNFusion graph and graph passes
  • [ ] Build graph with control-flow ops
  • [x] Loop op define
  • [x] If op define
  • [ ] Refactor graph passes for control-flow ops
  • [ ] Memory allocator
• Backend codegen